Some people see lust as the purest form of love. This viewpoint argues that being a pure emotional wish, based upon physical attraction, frees lust from the constraints of emotional baggage (or negative inner conceptual responses), and respects it for what it is, the direct emotional inner instinct and desire of one person, to carnally know and be intimate with another.

On the other hand, many people acknowledge that feelings of lust do not always imply feelings of love, and they make a strong distinction between the terms lust and love. Love in its pure form is said to be concerned with the well-being of the other, whereas lust in the average person is often more a product of their own libidinal urge than it is a product of a desire for the well-being of the objects of lust, although the two can certainly co-exist. Others, notably some asexuals, consider lust ultimately incompatible with, or unrelated to, love.

The aspect of lust as an inappropriate desire has led to its metaphorical extended use in other forms of desire to signify overwhelming desire or craving, such as a lust for power, success, or recognition. It has also been used in the sense of intense eagerness or enthusiasm, such as a lust for life.

In Catholicism, lust is subdivided into six categories: fornication, adultery, rape, incest, seduction, and unnatural vice.

Fornication and adultery are similar in that they both pertain to having sex outside of marriage. They differ in that the former pertains to situations where neither partner is married, whereas the latter pertains to situations in which one or both partners are married, but not to each other.

Rape is the act of forcibly penetrating someone without their consent. It is the responsibility of the victim, however, to use any means within his or her power to prevent the attack, otherwise it is not completely considered rape.
Incest is the act of sexual intercourse between individuals who are closely related, for example, those who are cousins, siblings, or between a parent and his or her child.

Seduction is the act of purposely inducing feelings of lust in someone else.

The unnatural vice consists of sexual acts that are sins against nature. This category is considered worse than the others because, while the others are sins against reason, the unnatural vice are sins against both reason and nature. The unnatural vice includes, but is not limited to, bestiality, which is considered the worst offense of lust, homosexual intercourse, masturbation, anal sex, oral sex, and any other form of non-unitive or non-procreative sexual gratification. However, some acts such as oral sex may be permitted in the context of marriage as foreplay, so long as it is used as a means and not as an end; the end, in this case, being that the man ejaculates inside the woman's vagina.